/*

    SDL - Simple DirectMedia Layer

    Copyright (C) 1997-2006 Sam Lantinga

    This library is free software; you can redistribute it and/or

    modify it under the terms of the GNU Lesser General Public

    License as published by the Free Software Foundation; either

    version 2.1 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,

    but WITHOUT ANY WARRANTY; without even the implied warranty of

    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public

    License along with this library; if not, write to the Free Software

    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

    Sam Lantinga

    slouken@libsdl.org

*/

#include "SDL_config.h"

#include "SDL_thread.h"

#include "SDL_timer.h"

#include <stdio.h>

#include <stdlib.h>

#include <sys/types.h>

#include <sys/ipc.h>

#include <sys/sem.h>

#include <errno.h>

#include "SDL_error.h"

#include "SDL_thread.h"

struct SDL_semaphore {

	int id;

};

/* Not defined by many operating systems, use configure to detect */

/*

#if !defined(HAVE_SEMUN)

union semun {

	int val;

	struct semid_ds *buf;

	ushort *array;

};

#endif

*/

static struct sembuf op_trywait[2] = {

	{ 0, -1, (IPC_NOWAIT|SEM_UNDO) } /* Decrement semaphore, no block */

};

static struct sembuf op_wait[2] = {

	{ 0, -1, SEM_UNDO }		/* Decrement semaphore */

};

static struct sembuf op_post[1] = {

	{ 0, 1, (IPC_NOWAIT|SEM_UNDO) }	/* Increment semaphore */

};

/* Create a blockable semaphore */

SDL_sem *SDL_CreateSemaphore(Uint32 initial_value)

{

	extern int _creating_thread_lock;	/* SDL_threads.c */

	SDL_sem *sem;

	union semun init;

	sem = (SDL_sem *)SDL_malloc(sizeof(*sem));

	if ( sem == NULL ) {

		SDL_OutOfMemory();

		return(NULL);

	}

	sem->id = semget(IPC_PRIVATE, 1, (0600|IPC_CREAT));

	if ( sem->id < 0 ) {

		SDL_SetError("Couldn't create semaphore");

		SDL_free(sem);

		return(NULL);

	}

	init.val = initial_value;	/* Initialize semaphore */

	semctl(sem->id, 0, SETVAL, init);

	return(sem);

}

void SDL_DestroySemaphore(SDL_sem *sem)

{

	if ( sem ) {

#ifdef __IRIX__

		semctl(sem->id, 0, IPC_RMID);

#else

		union semun dummy;

		dummy.val = 0;

		semctl(sem->id, 0, IPC_RMID, dummy);

#endif

		SDL_free(sem);

	}

}

int SDL_SemTryWait(SDL_sem *sem)

{

	int retval;

	if ( ! sem ) {

		SDL_SetError("Passed a NULL semaphore");

		return -1;

	}

	retval = 0;

  tryagain:

	if ( semop(sem->id, op_trywait, 1) < 0 ) {

		if ( errno == EINTR ) {

			goto tryagain;

		}

		retval = SDL_MUTEX_TIMEDOUT;

	}

	return retval;

}

int SDL_SemWait(SDL_sem *sem)

{

	int retval;

	if ( ! sem ) {

		SDL_SetError("Passed a NULL semaphore");

		return -1;

	}

	retval = 0;

  tryagain:

	if ( semop(sem->id, op_wait, 1) < 0 ) {

		if ( errno == EINTR ) {

			goto tryagain;

		}

		SDL_SetError("Semaphore operation error");

		retval = -1;

	}

	return retval;

}

int SDL_SemWaitTimeout(SDL_sem *sem, Uint32 timeout)

{

	int retval;

	if ( ! sem ) {

		SDL_SetError("Passed a NULL semaphore");

		return -1;

	}

	/* Try the easy cases first */

	if ( timeout == 0 ) {

		return SDL_SemTryWait(sem);

	}

	if ( timeout == SDL_MUTEX_MAXWAIT ) {

		return SDL_SemWait(sem);

	}

	/* Ack!  We have to busy wait... */

	timeout += SDL_GetTicks();

	do {

		retval = SDL_SemTryWait(sem);

		if ( retval == 0 ) {

			break;

		}

		SDL_Delay(1);

	} while ( SDL_GetTicks() < timeout );

	return retval;

}

Uint32 SDL_SemValue(SDL_sem *sem)

{

	int semval;

	Uint32 value;

	value = 0;

	if ( sem ) {

	  tryagain:

#ifdef __IRIX__

		semval = semctl(sem->id, 0, GETVAL);

#else

		{

		union semun arg;

		arg.val = 0;

		semval = semctl(sem->id, 0, GETVAL, arg);

		}

#endif

		if ( semval < 0 ) {

			if ( errno == EINTR ) {

				goto tryagain;

			}

		} else {

			value = (Uint32)semval;

		}

	}

	return value;

}

int SDL_SemPost(SDL_sem *sem)

{

	int retval;

	if ( ! sem ) {

		SDL_SetError("Passed a NULL semaphore");

		return -1;

	}

	retval = 0;

  tryagain:

	if ( semop(sem->id, op_post, 1) < 0 ) {

		if ( errno == EINTR ) {

			goto tryagain;

		}

		SDL_SetError("Semaphore operation error");

		retval = -1;

	}

	return retval;

}